Measurements of Three-Dimensional Acoustic Propagation over a Translationally Invariant Wedge and in a Scale-Model Canyon

date May 1, 2015
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Friday, May 1, 2015 4:00 p.m. in ETC 4.150

Dr. Jason Sagers
Applied Research Laboratories
The University of Texas at Austin

Scale model (1:7500) acoustic propagation experiments were conducted in a laboratory tank to investigate three-dimensional (3D) propagation effects induced by range-dependent bathymetry, with the objective of providing benchmark quality data for comparison with numerical models.  A computer-controlled positioning system accurately moved the receiving hydrophone in 3D space while a stationary source hydrophone emitted pulsed waveforms between 200 kHz and 2 MHz.  Acoustic measurements in two model environments are discussed.  First, experimental results are shown for a 1.22 x 2.13 m2 model bathymetric environment possessing a 44.5 mm deep flat bottom with a translationally invariant wedge of 10° slope along one edge.  Synthetic vertical line arrays (VLAs) were located on the wedge and mode filtering was performed at each VLA location to infer mode amplitudes.  Modal shadow zones are visible in the inferred range-dependent mode amplitudes.   Second, experimental results are shown for 1.19 x 2.13 m2 scale model representation of a portion of the Hudson Canyon.  The model was patterned after measured bathymetric data and fabricated from closed-cell polyurethane foam by a computer numerical control (CNC) milling machine.  Results are shown for propagation paths along and across the axis of the canyon where the received time series are post-processed to estimate travel times, transmission loss, and horizontal and vertical arrival angles. [Work supported by ONR].